1. Field of the Invention
The present invention relates to optical lens modules, especially to an optical lens module for use in, for example, a digital camera.
2. Discussion of Related Art
With the popularization of electronic products such as digital cameras, the requirements for the optical lenses employed therein is ever increasing. In order to provide high imaging quality, the development of the optical lenses mainly concentrates on the structure and configuration of the optical lenses.
As it is known to those with ordinary skill in the art, light travels at different speeds in different mediums. When a light beam obliquely enters a second medium with a refractive index n2 from a first medium with a refractive index n1, the direction of propagation of the light beam, at a boundary between the first and second mediums, will change. This change in the propagation direction is the so-called refraction phenomenon. Snell's law discloses that the ratio between the sine of incident angle and that of refractive angle is constant. This law can be expressed as below:n1 sinθ1=n2 sinθ2 Wherein n1 and n2 represent refractive indices of a first medium and a second medium, respectively. θ1 represents an incident angle, and θ2 represents a refractive angle.
According to Snell's law, when light transmits from air to glass, for example, the refractive index and shape of a lens are main factors in determining the deflection of the light. Accordingly, the development of the optical modules mainly concentrates on the refractive index and shape of the lens.
FIG. 6 shows such a focalization principle, using a conventional lens. This principle discloses that light can be focused and a formatted image can be formed with a lens having a proper shape and a smooth surface.
A lens module of a typical digital camera generally includes a plurality of optical lenses. Generally, in order to obtain a satisfactory imaging performance, the lens module commonly employs at least three optical lenses. Each optical lens is also referred to as a lens unit.
Referring to FIG. 7, a conventional lens/camera assembly includes a lens module 10, a sleeve 14, and a light-receiving unit 12. The lens module 10 and the light-receiving unit 12 are received in the sleeve 14. The light-receiving unit 12 is arranged at the focus of the lens module 10. The light-receiving unit 12 is configured for converting collected light signals into electronic signals.
The lens module 10 includes a plurality of lens units 102 received therein. Each lens units 102 has a different refractive index relative to the others. By such a configuration of the lens units 102, a relatively short focal length of the lens module 10 may be achieved. Therefore, the volume of the lens module 10 is relatively smaller. However, a plurality of lens units has to be employed, which increases complexity and costs of the lens module.
Accordingly, a compact lens module with a lower complexity and cost is needed.
Therefore, a heretofore-unaddressed need exists in the industry to address the aforementioned deficiencies and inadequacies.